Tube cleaning and nondestructive examination (NDE) are fundamental to heat exchanger performance maintenance.
Removing deposits from heat exchanger tubes in regular intervals can return flow and heat transfer to optimal levels. NDE is the most effective way to reduce tube failure, and methods like eddy current testing (ECT) and remote field testing (RFT) can identify tube vulnerabilities, like pitting and cracking, long before they lead to downtime and unplanned outages (see Figure 1). Smart maintenance allows for mitigation and repair, and can save plants hundreds of thousands of dollars in unplanned downtime and component replacement.
Turnaround managers look for speed and efficiency during the maintenance period. Ideal turnaround maintenance happens when there is a seamless integration of heat exchanger cleaning and NDE, so choosing one service provider with technology-based synergistic cleaning and testing capabilities yields the best results.
Maintenance managers understand the complications of employing two separate contractors for tube cleaning and NDE. A maintenance scenario with separate contractors for cleaning and testing can result in confusion and schedule delays. If the heat exchanger tubes are not cleaned well enough to proceed with NDE, an additional shift of cleaning will need to be conducted while the NDE crew waits. This illustrates the value of using one integrated service team that arrives prepared, informed and ready to work. It is most beneficial for the plant when this maintenance is done in tandem; NDE technicians must be nearby to confirm the heat exchanger tubes are test-ready, and one provider of both services can coordinate this all-important sequence.
Another impediment to fast and efficient heat exchanger maintenance is that some tube-cleaning methods involve extensive setup and a large site footprint. High-pressure water cleaning, in particular, requires a sizable footprint, and the significant water use requires time-consuming wastewater management.
Clean heat exchanger tubes facilitate reductions in the noise-to-signal ratio necessary for accurate data to be collected during NDE. Mechanical tube cleaning methods using low-pressure water have been found to result in cleaner tubes than conventional cleaning methods. What's more, the on-site footprint of mechanical tube cleaning is significantly smaller than that of methods like high-pressure water, because less equipment, less water and fewer technicians are needed (see Figure 2). Maintenance managers have reported the smaller footprint associated with mechanical cleaning methods supports an efficient turnaround schedule, because tubes are cleaned more effectively and quickly. This means the next phase, NDE, can begin on time. Turnaround managers understand that during these critical maintenance windows, the heat exchanger often is not the only component receiving maintenance. Mechanical cleaning is highly effective with smaller crews and less equipment, freeing up time and space for the completion of other maintenance projects on-site.
The process of heat exchanger tube cleaning and NDE cleans the tubes to improve flow and heat transfer and identifies the status of heat exchanger tubes, detecting damage before it becomes catastrophic. Knowing which tubes to plug or repair before they fail can save operators large sums of money. Today, there is a wide array of NDE testing for a variety of ferrous and nonferrous metal components. It is vital to choose an expert NDE service provider with an experienced staff of certified technicians using state-of-the-art equipment. All reputable NDE providers follow the stringent guidelines of the American Society of Non- Destructive Testing (ASNT). This organization exists to ensure continuity in quality of testing and consistent, repeatable results.
Turnarounds give us the opportunity to give important components like heat exchangers the maintenance they are overdue. A fast, efficient and synergistic maintenance protocol like mechanical heat exchanger tube cleaning and NDE provides comprehensive care that will optimize heat exchanger performance and prolong tube life.
For more information, visit www.conco.net or contact Beth Foley-Saxon at bfoley-saxon@conco.net.
